On 2014/2/18 18:28, Vegard Nossum wrote: > On 17 February 2014 03:34, Xishi Qiu <qiuxishi@xxxxxxxxxx> wrote: >> If we want to debug the kernel memory, we should turn on CONFIG_KMEMCHECK >> and rebuild the kernel. This always takes a long time and sometimes >> impossible, e.g. users don't have the kernel source code or the code >> is different from "www.kernel.org" (private features may be added to the >> kernel, and usually users can not get the whole code). >> >> This patch adds a new command-line "kmemcheck=3", then the kernel will run >> as the same as CONFIG_KMEMCHECK=off even CONFIG_KMEMCHECK is turn on. >> "kmemcheck=0/1/2" is the same as originally. This means we can always turn >> on CONFIG_KMEMCHECK, and use "kmemcheck=3" to control it on/off with out >> rebuild the kernel. >> >> In another word, "kmemcheck=3" is equivalent: >> 1) turn off CONFIG_KMEMCHECK >> 2) rebuild the kernel >> 3) reboot >> >> The different between kmemcheck=0 and 3 is the used memory and nr_cpus. >> Also kmemcheck=0 can used in runtime, and kmemcheck=3 is only used in boot. >> boottime: kmemcheck=0/1/2/3 (command-line) >> runtime: kmemcheck=0/1/2 (/proc/sys/kernel/kmemcheck) > > This is not the right way to do what you want. > > The behaviour that we want is: > > - CONFIG_KMEMCHECK=y + kmemcheck=0 (boot parameter) should have a > minimal runtime impact and not limit the number of CPUs > - CONFIG_KMEMCHECK=y + kmemcheck=1 should limit the number of CPUs during boot > - setting kmemcheck to 1 via /proc/sys/kernel/kmemcheck should > probably return an error if more than 1 CPU is online > > > Vegard > Hi Vegard, Thank you for your reply. If we only use "kmemcheck=0" to control, how about the used memory? Will it use about twice as much memory as normal? Thanks, Xishi Qiu > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>